Method and apparatus for broadcasting and receiving radio signals



H. C. DEVORE Oct. 27, 1931.

METHOD AND APPARATUS FOR BROADCASTING AND RECEIVING RADIO SIGNALS Filed Aug- 1926 DE TEcroR INVENTOR 14 w W44 FWiQi HENRY (3. DE vonn,

interfering with one another.

Patented Oct. 27, 1931 U ire as orrlca or MONONGAEELAQ PENNSYLVANIA, ASSIGNOR 'ro anna}: 3. DE vonnor-wrnmmc'ron, DELAWARE METHOD AND a'rrance'rnsron nncancnsrrns annencnivme RADIO s'rsnnn's I Application filed August 24, 1926. Serial No. 131,182.

This invention'relates to the transmission of signals by radio and is pariicularly adapted. to radio telephony. v

In the broadcasting of programs by radio considerable difficulty is encountered in providing for a suflicient number of stations in the permissive band-of wave lengths. The range of wave lengths between which broadcasting stations can operate is necessarily restricted, and if there is to be no overlapping,-

each station must have a wave length different from every other station, and the degree oi separation in the wave lengths between stations must be appreciable. This necessarily-means'that onlya very definite number of stations can operate at the same time. The number of stations which can operate-at the same time, is far below the number of stations that actually exist, and a very considerable difiicu'lty is encountered in providing for the establishment of new stations. This is imposing a considerable restriction and limitation in the use ofradio.

The, present. invention has for its primary obj ec'tto provide a system whereby the range of broadcasting can be increased between the maximum and'minimum limits now provlded so that morestations can broadcast without The invention contemplates primarily thatv the broadcastlngstation shall simultaneously transmit its program on two or more wave lengths. With different combinations of two or more wave lengths the mathematical pro gression is such thatseveral thousand broadcasting stations could operate without. interferen-ce, where,- at the present-time, therange permits of only stations.

a few hundred broadcasting -That two stations can broadcast the same program simultaneously on two or more wave,

lengths is well known,'-,and is at the present time practice It is also well known that several stations may simultaneously broadcast 1 S me program onfdifferentwave lengths, and the present invention is also applicable to such a system of broadcasting.

According to' the present invention-it is roposed to provide means at the receiving end of the circuit which would respondt'o its the upper wave limit is reached. 'Anot'her series of stations wouldopelete with combinations of E225v meterwave-lengths and-another wavelength, as, for instance 225 meters and 1250 meters. Other series of stations I would operate onother combinations offwave lengths in the same" way. "-With the present in vention,assuming it was desiredto tune in on that, station broadcasting 0113-200 and; 225 meter Wave lengths, -.none. of; v the; other stations having a 200 meter wave length as one of its wave lengths or havinga 225 meter wave length as one of its wavelengths would interfere with the program being;received.

Another exampleof the. use otmy invention isthe simultaneousv receptionsof two or more stationsbroadcasti ng the same program simultaneously on different wave lengths. Signals (other than those desired) which may be broadcast on any of the wave lengths common to those being received are selected out, so that onlythe'desired signals pass through the receiver to the translating device used.

g The inventionmay be more readily understood by reference to the accompanying drawing which illustrates diagrammatically a receiving circuit embodying my invention.

At the receiving station there are two in'dependent receiving sets, one ofwhich is designated A an'dthe other of which is designated B; .These receiving sets may be of any known orpreferred" type, and in the drawing they have been only schematically illustrated; Each receivin set has a rectifier therein,12,designating t'ierectifier of; the a i set A? and .3 designatingthe rectifier of the set-B. I These rectifiers are indicated as all! 7 purpose of quency amplifier means 21 1s only schema- .1-

being preferably, but not necessarily, of the thermionic type. In the illustrated example each rectifier has an anode which is in circuit with a source of direct current, these sources of direct current being designated 4 and 5 respectively. In series with the anode of the rectifier 2 are two coils 6 and 7. Coil 6 is inductively disposed with respect to a coil 8 and coil 7 is inductively disposed with respect to coil 9. The direction of a current flow in coils 6 and 7 is preferably the same.

The output or anode of the rectifier 3 is in series with a coil 10, also inductively disposed with respect to coil 8 and coil 11, which is also inductively disposed to coil 9. The coils 6 and are of the same value, and the coils 7 and 11 are of the same value, but the direction of current flow through the coil 10 is re versed with respect to the current flow through the coil The direction of current w in the coil 11 is the same as the direction of current iiow in the coil 7. As thus ar- Pill 6d the fields of coils 6 and 10 tend to n' utralize each other so as to induce no current through the coil 8, while the eiiect of the coils 7 and ll is to work together to induce a 'wre'wt flew in the coil 9.

While the electrical characteristics of coils 8 and 9 are not necessarily the same as the electrical characteristics of coils 6, 7, 10 and 1-1. the var'ous coils are preferably of such value and are sodisposed that, for a given voltage value and frequency, the inductive effect of coil 6 or 10 on coil 8 will be the same as the inductive effect of coil 7 or 11 on coil 9.

The opposite ends of the coil 8 are connected with the control electrodes orgrlds of the electron relays 12 and 13 respectively. The output sides of anodes of these relays 12 and 13 are connected together and are in series with a source plate voltage 14. Included in the output circuit of the relays 12 and 13 is a coil 15,'whose other side iscon nected to the cathode terminals of the respective relays 12 and 13.

The coil 9 is similarly coupled with a c011 16 through thermionic relays 17 and 18. At 19 is indicated the source of plate voltage for 'the electron relays 17 and 18. The coils 15 and 16 are inductively disposed with respect to a coil 20, but the direction of current flow through the coil 15 is reversed with respect to the direction of current flow 7 h ough the coil 16, so that the magnetic fields ofthe two tend to neutralize each other in their inductive effect on the coil 20. The coil 20 may be in circuit with a telephone or other translating device, .either directly or through any suitable audio-frequency amplifying circuit such as that indicated diagrammatically at 21.- The telephone or translating device is designated-22. For the simplification the audio-frecally indicated, as this in itself forms no part of the present invention and is now well understood by those skilled in the art.

The operation of the circuit may now be traced. Assume that a station to be received is broadcasting both on 200 meter wave lengths and 225 meter wave lengths. Set A is tuned to receive the signals at 200 meters and set 13 is tuned to receive the signals at 225 meters. Flowing through the coils 6 and 7 is an undulatory direct current whose undulations correspond to the received signal impulses, and flowing through the coils 10 and 11 is a similar undulatory direct current.

Coils 7 and 11 will act in conjunction to induce a current flow through the coil 9. This current flow through the coil 9 will correspondingly modulate a current flow through the coil 16 and the coil 16 will induce a corresponding current in coil 20 which will be made audible in. the translating device 22.

It will be apparent that the same action takes place when the different wave lengths are received from different stations, the same signals, of course, being broadcast simultaneously on the different wave lengths.

Now assume that set A, in addition to receiving the station which it is desired to receive, is also receiving a second station which also has a 200 meter wave length as one of its broadcasting wave lengths. Set A will necessarily respond to this second station as well as to the first. This will mean that in addition to thesignals which it is desired to receive, there will be other undulations in the current in the coils 6 and 7. These other undulations will not be correspondingly set up in the coils 10 and 11 because set B is tuned to respond to 225 meters. The disturbing undulations passing through the coil 8 will not be neutralized by the field of the coil 10 so that a current will be induced in the coil 8 corresponding to the undesired undulations passing through the coil 6. The undesired undulations of the second station will also inductively efi'ect coil 9, so that a current will flow through coil 16 which undulates both in accordance with the desired station and the undesired station. The currents induced in coil 8, corresponding only to'the undesired undulations of set A, will cause a correspondingly undulating current to flow through coil 15; Coils 15 and 16 act in opposition, so that there will be induced in coil 20 acurrent flow correspondin only to the desired undulations of the first station, While the undesired undulations of the second station will be balanced out, and the telephone 22 will be actuated only in accordance with the signals which both sets A and B are simultaneously receiving. In the same way, any signals which are disturbing to set B that are not received in set A will be correspondingly neutralized.

If the signals received on one wave length type are stronger than the sandesignals on other wavelengths,'-the excess strength over-the weaker signal will be neutralized in the receiver, and the signals in coil will (when using two sets such as A and B" be twice be used which'pr'oduces a flow in coil 15 or 16 proportional to the flow in coils-or 8, it being desirable, ofcourse, to avoid distortion. If thermionic tubes are used, as illustrated, care should be taken that theyare operated on the proper portion of their characteristic curves so that an increase in current flow in one Wlll bes-ubstantially compensated for by a corresponding decrease in current flow of the other to avoid distortion. r

The advantages of the invention arise from the fact that the number of broadcast ing stations which can operate within a giyen range can be very effectively increased without one station interfering with another. It will be seen that the only time that there can be any interference would be when two stations having one of their two wave lengths common would broadcast the same note at exactly the same time, in which case there might be some increase noticeable in the out.- put of the telephone, but these occasions would necessarily be rare, and if, instead of having but two sets A and fB there were three or more sets, the chance of this h appening could be even more effectively reduced. Not only will the present system tend to eliminate interference with other stations, but will tend to reduce the interference produced by local and other disturbances, to some extent. For instance,-the antennas for the two stations could be at right angles or widely separated so that they would not respond to the same extent to static or other disturbances, and a more quiet reception could be secured.v

While it is realized that it might, for sometime, be impractical to immediately have all broadcasting stations transmit on two wave 1 lengths, it is possible that a certain section in the available bands of wave lengths could be allotted to stations desiring to use the resent method. This could be done without injury to he present system and without rendering all present receiving equipment 0bsolete. As a matter of fact the arrangement indicated in the drawing could be assembled in a case with jacks for plugging into the detector or audio-frequency output of sets of the present type.

It will be apparent that the diagrammatic illustration does not define th'e'limits of my invention,'but that the coils may be variously disposed and the circuits altered to carry out illustrated, since any desireddevice may the principles involved and; obtain the ad.- vantageous results. j a f While I have described and illustrated one proposed embodiment of my invention, it

will be understood that'theinvention is not restricted to use with only two receivingsets, as'the. invention is applicable to the arrangement wherein a station could broadcast on three or four or more wave lengths, and various changes and modifications may be made currents not common to all of the signals being separately received. 7 2. A system for receiving and translating radio signals which are simultaneously broadcast on a plurality ofgdifferentwave lengths while neutralizing any signals not common to all of the wave lengths being received including means. for rectifying re: ceived signal impulses on separate wave lengths, a circuit, responsive to all impulses which are rectified, a circuit responsive only to signals whichare not common to all of the wave lengths being received, said circuits being oppositely coupled to a translating circuit whereby signal impulses in the secondv circuit are neutralized by the corresponding impulses in the first circuit. 1

A system for the reception of the same radio signals simultaneously transmitted on a plurality of wave lengths without interference, including a separate receiving circuit: for each wave length on which the signal is broadcast, each receiving circuit having its output inductively impressed on two local circuits, oneof which responds to all of the impulses in, the several output circuits and.

the other of which responds to only those impulses which are not common to all of the output circuits of: the several receivingxcincuits, and a translating circuit to which the two local circuits are inductively coupled in reverse phase relation whereby like current values in the two circuits, are neutralized by each other and the translating circuit caused to respond to the; difference.

4-. A system for the reception'of the same radio signals simultaneously transmittedon a plurality of wave lengthsfwithout interference which consists in a receiving circuit having a receiving set for each wave length on which the signal is broadcast, each receiw ing set having an audio-frequency output, local circuit into which the audio-frequency impulses of the severalstations is impressed,

a second local circuit which responds only to those audio-frequency currents in the several receiving circuits which are not common to all of the receiving circuits, said local circuits being inductively coupled in reverse phase relation to a translating circuit whereby like current impulses in the two local circuits are neutralized and the translating circuit caused to respond to the difference in the current values in the two circuits only.

5. A system for the reception of the same radio signals simultaneously transmitted on at least two wave lengths, including at least two separate receiving circuits, each having a rectifier, one receiver'having its rectifier output passed through two coils wound in the same direction, the other receiving circuit having its rectified output passed through two other coils, one of which is wound reversely to one of the coils of the first circuit and one of which is wound the same as the coils of the first circuit, a coil inductively interposed in the fields of the oppositely wound coils of the respective receiving circuits, a second coil inductively interposed between the like coils of the respective receiving circuits, a translating circuit, and means for inductively impressing current impulses induced in said first and second coils in reverse phase relation on the translating circuit, current impulses of like value induced in the first and second coils thereby being neu tralized and the translating circuit caused to respond only to current impulses which are different from those induced in the first coil only. r

6. A system for the reception of the same radio signals simultaneously transmitted on at least two wave lengths, including at least two separate receiving circuits, each having a rectifier, one receiver having its rectifier output passed through two coils wound in the same direction, the other receiving circuit having its rectified output passed through two other coils, one of which is wound-reversely to one of the coils of the first circuit and one of which is wound the same as the coils of the first circuit, a coil inductively interposed in the fields of the oppositely wound coils of the respective receiving circuits, a second coil inductively interposed between the like coils of the respective receiving circuits, an electron relay circuit connected across the terminals of the first coil, a second electron relay circuit connected across the terminals of the second coil, a separate coil in the output sides of the electron relay circuits for said first and second coils, said last'named coils being effectively reversed, whereby their fields tend to oppose each other, another coil inductively disposed with relation to said last named coils, and la translating device responsive to current impulses in duced in said last named coil.

7. A system for the reception of the same radio signals simultaneously transmitted on at least two wave lengths, including at least two separate receiving circuits, each having a rectifier, one receiver having its rectifier outputpassed through two coils wound in the same direction, the other receiving circuit having its rectified output passed through two other coils, one of which is wound reversely to one of the coils of the first circuit and one of'which is wound the same as the coils of the first circuit, a coil inductively interposed in the fields of the oppositely wound coils of the respective receiving circuits, a second coil inductivelyinterposed between the like coils of the respective receivingcircuits, a translating circuit, an elec tron relay circuit for each or" said first and second coils, the output of said electron relay circuits being inductively coupled in reverse phase relation to the translating circuit.-

In testimony whereof I have hereunto set my hand.

H. C. DE VORE. 

